The hacker group Anonymous claimed Tuesday to have taken out 5,500 Twitter accounts linked to the Islamic State group, which claimed responsibility for the Paris attacks.

The loosely organized hacking collective made the claim in a tweet one day after launching #OpParis campaign, which stepped up an earlier effort to shut down social media accounts of the organization.

“We report that more than 5500 Twitter account of #ISIS are now #down! #OpParis #Anonymous #ExpectUs,” said a tweet posted on Tuesday which followed a video message posted Monday.

It was not immediately clear how the accounts would have been disabled. But the hacker group said it posted the accounts to an online forum labeling them as #daeshbags, a reference to Daesh, an Arabic acronym for the Islamic State group.

In an apparent riposte, a message posted via the messaging service Telegram calls on Islamic State affiliates to secure their Internet communications.

“The #Anonymous hackers threatened… that they will carry out a major hack operation on the Islamic state (idiots),” the message said.

Anonymous has waged a long-running campaign against the Islamic State group but stepped up the effort following the attacks last Friday in the French capital.